1. Field of the Invention
The present invention relates to a method and apparatus for processing an image and also to a storage medium in which an area representing a particular image is detected from a series of moving frame images.
2. Description of the Related Art
In moving image transmission systems such as a video telephone system and a video conference system, an important image to transmit is a human image. In particular, a high-quality face image is needed to be transmitted in a compressed fashion. In order to efficiently use communication bands, where a human face area is assigned a large number of codes, the number of codes assigned to a background area is greatly reduced so as to reduce the total number of codes while maintaining the image quality to a desired level. To this end, extraction means is required for accurately extracting a face area at a high speed.
Various techniques for extracting a human face area from a two-dimensional image have been proposed. Hagiwara et al. have proposed a technique of modeling the contour of a face using an ellipse and searching for the face area according to a genetic algorithm (Yokoo, Hagiwara, xe2x80x9cExtraction of a Plurality of Face Areas from a Natural Image Using a Genetic Algorithmxe2x80x9d, Journal of the Institute of Electrical Engineers of Japan, Vol. 117-C, No. 9, pp. 1245-1252, 1997). Hara et al. have proposed a technique of detecting a face area by means of matching with a template of a face according to a genetic algorithm (Hara, Nagao, xe2x80x9cExtraction of a Face Area in an Arbitrary Direction in an Image Using GAxe2x80x9d, Technical Report HCS97-12, pp. 37-44, 1997, the Institute of Electronics, Information, and Communications Engineers).
The above-described techniques using the genetic algorithm allows high-accuracy detection. However, the problem of these techniques is that a large number of computing processes are required, and thus these techniques cannot be employed to process a moving image in a real time. Japanese Patent Laid-Open No. 10-21394 discloses a technique in which preprocessing is performed to roughly determine an area to be searched on the basis of hue information and then only the obtained area is searched by means of pattern matching according to a genetic algorithm thereby achieving high-speed searching. However, even this technique still needs a large amount of computation in the preprocessing. Another problem of this technique is that features of a moving image are not effectively utilized.
In view of the above, an object of the present invention is to provide a technique of accurately and quickly detecting an area representing a particular image from a moving image.
The above object can be achieved by the present invention having various aspects as described below.
According to a first aspect of the present invention, there is provided an image processing method for determining an area representing a particular image from a moving image using a genetic algorithm, the method including the steps of: extracting a current frame image from a series of moving image data; producing a plurality of initial chromosomes indicating the particular image from a frame image previous to the current frame image; and determining the area of the particular image in the current frame image by executing a genetic algorithm on the initial chromosomes.
According to a second aspect of the present invention, there is provided an image processing method for determining an area representing a particular image from a moving image using a genetic algorithm, the method including the steps of: extracting a frame image from a series of moving image data; a first production step for randomly producing a plurality of initial chromosomes including a parameter indicating the particular image; a second production step for producing a plurality of initial chromosomes including a parameter indicating an area of the particular image; determining an evaluation value indicating the fitness, to the frame image, of the plurality of chromosomes produced in the first and second production steps; a selection/reproduction step in which a chromosome having a low evaluation value is removed from the plurality of chromosomes, and a chromosome having a high evaluation value is reproduced; performing crossing-over with a predetermined probability upon a plurality of chromosomes obtained in the selection/reproduction step; performing mutation upon a plurality of chromosomes obtained in the crossing-over step; and a determination step in which, if a chromosome is obtained which has an evaluation value greater than a predetermined threshold value under a predetermined condition after iterating the evaluation step, selection/reproduction step, crossing-over step, and mutation step, a parameter represented by the chromosome is determined as a parameter representing the area of the particular image of the frame image.
Further objects, features and advantages of the present invention will become apparent from the following detailed description of embodiments of the present invention with reference to the accompanying drawings.